Wireless telegraphy



F. CUTTING AND B. WASHINGTGN.

WIRELESS TELEGRAPHY.

AvPLlcATloN FILED DEc,4,1916.

Patented .my 6,1920.

WlTNESSES PATENT OFFICIEL emmen mummy-mm FULTON CUTTNG, 0F TUXED PARK, NEW YORK, AND BOWDEN WASHINGTON, OF

' CAMBRDGE, MASSACHUSETTS. l

TNR'ELESS TELEGRAPHY.

Specification of Letters fatent.

Patented July 6, 1920.

appiieauoa filed December e, 191e. sensi No. 134,312.

Massachusetts, have invented a new and uses ful lmprovement in 1Wireless' T elegral'ihy, of which the following is a full, clear, and exact description, reference being had to the accompanying drawings, forming part of this specification, in which- Y Figure l is a conventional diagram showing one embodiment of the apparatus, and

Fig. 2 is a 'diagrammatic illustration show'- ing `in a Ageneral way the relation between the various currents in the al'niaiatus.

The present invention relates to wireless telegral'ihy, and more particularly to increasing the Veiiliciency in the production of radiated wave trains ofv an audible fre quency, and at the same time producing a clear audible vnote in the receiving station.

In the usual construction of quenched gap sets, it is well known that to haveia` clear note at the receiving station there should not be more than one spark per alternation or half cycle of the alternator. Five hundred cycle sets are usually huilt to spark oncefor each alternation, thus giving a thousand cycle note. lt has been found that when such a set is operated to give two or three sparks per alternation, the note becomes bad. Vonsequently, the practice has been to so vproportion the condenser and discharge gap to theI feed current that but a single condenser discharge occurs' for each alternation of the alternating current.

'ille have discovered, however, that a plurality of condenser discharges for each pulsation or alternation may be advantageously employed under certain conditions. If a suitable shaped feed current wave be employed, and the apparatus adjusted to give a sufficient number of. condenser discharges per alternation, the condenser discharges will take place in separate or discrete groups,

separatedby periods of inactivity, and. the

general shape or outline of the radiated' power wave will correspond approximately to the shape or outline of the feed current. Under these conditions a `cleary tone and 'maxinnunxeifect are obtained at the `tele-` phones of the receiving station. Th note at the receivingstation can be made as clear,

if not clearer7 than that obtained with the best tive hundred cycle set operated with but a single discharge per current alternation. The wave of power acting on the tele phone diaphragms of the receiver has ap proximately the durationof an alternation of the feed current and is much better suited to set the diaphragms into vibration thanA The condenser discharges or impulses pass through the primary 4 of the transformer 5, the secondary 6 of which is included in an antenna or oscillation circuit 7. The circuit including the gap 3 'and primary 4 may, for convenience, be designated as the discharge circuit 8, while the circuit including the a1- ternator l and the sending switch 9 may be designated as a feed circuit 10.'

The capacity of the condenser 2' and break-down voltage of the gap 3 are so proportioned-with relation to the feed current thatA ai plurality of discharges take place for cach half cycle or alternation of the feed current. The number of discharges per alternation will vary depending upon the wave shape of the feed current and the type of the set. In using the usual commercial form of alternator supplied for five hundred cycle sets, we have ,found that from twenty to thirty discharges per alternation give vgood results on a one-half kilowatt five hundred cycle set. Vith the usual commercial type of alternator, the'lower limit appears to'be about eight Acondenser discharges per alter-- nation, below which audible andvundesirable harmonics begin to occur. alternatorbe employed having a wave shape such that the peaks of the waves are separated by periods of substantiallyno current flow, such, for example, as .the wave shape indicate'dat F in Fig. 2 of the drawings, it

is possibleV to 'reduce Wear.-

denserfdischargepe'falternation-below this However, if an ,Y

' discharges clear tone with four limit and to obtain a condenser discharges the feed current. The peaks orportions of the waves of suflicient voltage to excite the discharge gap are separated by periods olf very low voltage and, consequently of substantially no'current flow to the condenser,

so that -the resultant groups of condenserA discharges and radiated oscillations are discrete, that is, separated by substantial intervals of inactivity from the next preceding and succeeding groups. This allows an opportunity for the diaphragm of the receiving telephone, which is energized by the received group of radiant oscillations, to swing back before it is again energized.

ln Fig. 2 is illustrated diagrammatically what is believed to be the general relation between the feed current, and the secondaryor antenna current.- It is to be understood that these diagrams are not intended to be exact, but are presented for the purpose of more graphically presenting what we believe the current phenomena to be. These diagrams and their description are for the purpose of description, and they are not intended to limit the invention to the current relations therein shown.

The alternator 1 preferably produces a feed current F having the wave shape shown at the top of Fig. 2. It will be noted that this feed current has a peaked wave shape, the current decreasing substantially to zero after the p'eak and remaining there for a period, the duration of which is approximately the 4same as that of the current wave itself. As the condenser 2 is charged, the gap '3 breaksl down whenever the condenser voltage reaches 'that of the break-down voltage of the gap. The condenser voltage is indicated diagrammatically by V in the second .line of Fig. 2, in which condenser voltage is illustrated as gradually increasing until a discharge takes place, then increasing again until a second discharge takes place, and so on. The frequency of the condenser discharges, of course, varies, depending upon the feed current, the condenser being charged and discharged more rapidly when the feed current is at or near its maximum. The current in mary c1rcu1t is 1n the form of discontinuousthe discharge or pri- The generator wave indif duced current, the condenser voltage, the primary or discharge circuitv tained the envelop current impulses, indicated'at D in the third line of Fig. 2. During the positive alternation or halfcycle of the current these discharges will take place in one direction, while during the negative half cycle of the feed current the discharges D will take place in the opposite direction. Each discharge or current impulse Din the primary induces a train of oscillations in the secondary or antenna circuit, as indicated at O in the fourth or bottom line of Fig. 2. `Each train of oscillations tends to die out. However, when the condenser Vdischarges'take place with increased frequency, as during the maximum of the discharge current F, the succeeding condenser `discharges serve to boost the declining oscillations already in the oscillation circuit, and thereby increase them, i

trains. This outline or envelop of the group has substantially the same shape as the envelop or outline of the wave of power proinI the oscillation circuit and radiated therefrom.

The current relations shown in Fig. 2 are those believed to exist in apparatus built by us as a modification of the Chaffee system shown in patent to Emory L. Chaffee, No. 1,189,7 91. The system built by us employed Chaffees system of impulse excitation with substantially perfect quenching, and with the approximate one and seven tenths to one ratio between the natural period of the primary or feed current circuit and the natural period of the secondary or oscillation circuit, described in the Chaffee patent, but with a symmetrical discharge gap and an alternating instead of a direct lfeed current. In this system the secondary oscillations preferably overlap, the succeeding condenser discharges serving to boost and lin Athe oscillation or antenna circuit.

`Since the activity of the high frequency circuits is substantially proportional to the feed current, an antenna radiation is obor general outline of which is similar in shape to that of the alternating feed current rectified. Since the gap we employ is symmetrical, both the positiveV and negative alternations vof, the alternating feed current produce the same effect on the high frequency circuits. AS the feed current increases from zero the condenser charges and discharges. At first this takes place slowly, but at an increasing rateas the feed current approaches andreaches `its maximum. The frequency of occurrence of the primary impulses or discharges 1s therefore proportional to the feed current.

shape or smoothed-out lcontour or outline of the group of oscillation root ofthe 'frequency of the primary impulses or discharges, it can be seen that the antenna` current is approximately` proporf tional to the square root of the feed current, or the power in theantenna is approximately proportional to the feed current. This relation, while approximate, is not to betaken exactly, sincevthe antenna current is continually dying down between the primary discharge impulses. ln apparatus in which the secondary oscillations die down between the primary discharge impulses, instead of overlapping and boosting as shown in the illustrative diagram, similar results will be obtained, because the power radiated from the antenna will be approximately proportional to theY frequency of the primaryl impulses, so that the power wave will have the general shape of the feed current wave. WVhat the power wave is may, perhaps, be made clear by the following considerations: There are in the system three periodicities each different from the other. There is the generator frequency, the discharge frequency (whichv varies), and the antenna frequency., The antenna power maybe viewed from all of these frequencies.

From the point of view of the antenna fre.

quency we have the actual instantaneous power varying at the same rate as the antenna oscillations. From point of view of the discharge frequency, we have a aower function which increases, rapidly uring each condenser discharge, dies down between discharges and is renewed or boosted at the next discharge. The contour of such a wave vis therefore saw-toothed. Lastly, if we neglect the saw-teeth of this power wave, we get a power wave which is similar in shape to the feed current wave. yIt is the values or ordinates of this power wave, (the smoothed-out contour of the saw-toothed wave) which are approximately proportional to the values or ordinates'of the feed current vtaken at corresponding instants of It is found that a feed current Wave of the same general form as that shown in Fig. 2 is most efficient for operating the telephones at the receiving station. A wave of this sort is arpeaked wavelwhich drops to substantially Zero and remains at a substantiallyzero value for a period about equal in duration to that of the current waveit-self (that is, neglecting small values yinsufficient -to induce gapy activity). With such a wave the periods of'gap activity areabout equal to thel periodsv of inactivity. The resultant rqroups of radiated waves therefore have substantially the same shape and duration as the feed current wave rectlfied, the power gradually increasing to a maximum, then l gradually decreasing to zero and remaining at zero for a period substantially equal to the' length of the wave, and again increasing to a maximum and dropping Ato z'ero.. lVhile the antenna oscillations never actually cease, they are'generally looked upon as having ceased or, become zero. when theyA have died down to an unimportant value, so that it will be understod that although the antenna oscillations do not absolutely cease during the periods of 'gap inl activity, yet, as a practical matter,.they may be looked upon as having ceased. This relationship between the groups of wave trains,

namely, Athat the duration of the groups of wave trains is about equal to the interval between the groups, is found to be of great advantage in the eicient operation of the telephones at the receiving station. 'With the apparatus of the present invention it has been found rthat four ti-mes greater audbility with a five hundred cycle set was obtained than when such set was operated with but a single spark per current alterna tion.

Other advantages obtained in the present system are, the low frequency power circuits are 'simpler and more advantageous, because lower voltages may be employed, no adjustment or resonant condition is needed between the capacity and inductances of the low frequency power circuits, the transformer usually employed between the generator and the condenser may be discarded if desired, the condenser losses due to the rapid charging of the condenser are much -lower than when the condenser is charged for each alternation of the feed current, and the lower discharge voltage permits the use of a condenser with a much smaller quantity of dielectric 'than required with the higher discharge voltages necessary for but a single condenser discharge peralternation. Moreover, the purity of the tone at the receiving' station is stable and is obtained inherently in the transmitting apparatus and without careful adjustment. .A few condenser dis'- `charges more "orl less for each 'alternation does not disturb the purity of the tone, whereasv with the ordinary five hundred cycle set if the number of condenser discharges increases beyond one per alternation the purity of the tone is destroyed.. Greater audibility for the same power is produced at the receiving stations when the telephones are 'employed for receiving, due to the fact that the telephones -work 'more efficiently under aweak sustained force than under a strong' force ofA a'short duration, and as above "pointed out, the waveshape of the alternator maybe so adjusted that the power radiated by the antenna, which ive-similar in l charges occur when the condenser'is charged to a voltage sufficient to break down the resistance of the discharge gap, and the in-4 dividual discharges are separated by intervals of no gap activity, during which intervals'the condenser is accumulating a new charge preparatory to another discharge. We are aware of the patent to McCaa No. 1,211,863, issued Jan. 9, 1917, and do not claim What is therein shown.

While We have illustrated and described one specific and preferred form of apparatus for carrying out the present invention,

other forms and constructions of apparatus n may be employed. For example, instead of the Chaffee gap, a quenched gap of the more usual constructiony may beemployed. Also, instead of an alternator for supplying the pulsations which charge the condenser and which give the tone at the receivingstation, other means for producing the pulsations may be used. It is to be understood therefore that the invention is not limited to its illustrated embodiment, but may be embodied in otherapparatus anl methods Within the scope of the following claims.

We claim:

1. Apparatus for producing electrical oscillations having an ,audible group frequency, comprising, an oscillation circuit, and means for producing oscillations therein comprising a discharge circuit coupled with the oscillation circuit and including a condenser and' a discharge gap, and means for supplying a pulsating feed current to the condenser-,the capacity'of the condenser and the break-down voltage of the gap being so proportioned that la sufficient number of condenser discharges occur foreach pulsation of the feed current to produce a radiated power Wave having an envelop of .substantially the same shape that of the feed current pulsation, substantially as described.

2. Apparatus for producing electrical os- 'cillations having .an audible group frequency, comprising, an oscillation circuit, and means for producing oscillations therein comprising a` discharge circuit coupled with the oscillation circuit and .including a condenser and a discharge gap,` and means for supplying a pulsating feed current to the condenser, the capacity of the condenser and the break-down voltage of the gap being so proportioned that a plurality of discharges occur for each pulsation of the feed current,

the discharge frequency varying and being substantally proportioiml to the feed current whereby the power in the osclllatlon clrcomprising, an oscillation circuit, and means for producing oscillations therein comprising a discharge circuit coupled with the oscillation circuit and including a condenser and a discharge gap, and means for supplying a pulsating feed current to the condenser, the capacity ci' 'the condenser and the lbreakdown voltage of the 'gap being so proportioned that a plurality of discharges occur for each pu'lsat'ion of the feed current and the envelop of the radiated po r Wave has substantially the same form ai duration as the feed current pulsations, the feed current pulsations having vsuch duration that the periods of gap activity are about equal to the periods of inactivity, whereby groups of Wave trains are produced which will act efficiently on the telephones at the receiving station, substantially as described.

4. Apparatus for producing electrical oscillations having an audible group frequency, comprising, an oscillation circuit,

in comprising a discharge circuit coupled with the oscillation circuit land including a condenser anda discharge gap, and an alternator for supplying an alternating feed currentv to the condenser, the capacity of the condenser and the break-down voltage of the gap being so proportioned that a sufl'ici'ent number of condenser discharges occur for eachalternation or half cycle of the feed current to' produce a power Wave in the oscillation circuit having an envelop ofl substantially the same shape as that of the alternating feed current, substantially as described.

5. Apparatus for producing electrical oscillations having an audible group frequency, comprising, an oscillation circuit,

lthe feed current' alternations orf' phases, the

alternator having a peaked u'ave ofsuch shape that the periods of gap activity are substantiallyf equalto those of inactivity. substantially as described.

(i. The method of producing electrical oscillations having an audible group fre- (uiency,r comprising` charging a condenser with a pulsating current, discharging theconl' denser a plurality of times foreach feed current pulsation, and causing the condenser discharges to produce trains of radiated Wavesor oscillations, the envelop of the power Wave of eachjgroup of wave-trains having approximately Ythe shape and duration' of lthe ,condenser charging current pulsations, substantially as described.

. The method of producing electrical oscillations having an audible group fre-v quency, comprising, charging va condenser with a pulsating -current the Wave shape of which increases to a maximum and then diminishes substantially to zero, discharging lthe condenser through a dischargeci-rcuit coupled with an oscillation circuit so as to produce a train of oscillations in the oscillation 'circuit for each condenser discharge, the discharge frequency -of the condenser varyingand increasing and decreasing according to the wave shape of the pulsation, whereby the power in the oscillation circuit increases to a maximum and then decreases to zero approximatelythe sameas the feed current pulsation,substantially as described.

8. Apparatus for-,producing electrical os- Ycillations having an audible group frequency, comprising an oscillation circuit,'and means for producing oscillations therein l comprising a discharge circuit including` a condenser and a discharge' gap, and means for supplying a pulsating feed current of an audible frequency to the condenser hav- A ing its current pulsations separated by intcrvals of little, if`any, current flow, vsaid intervals bein'g comparable in duration to the current pulsations, the capacity of the condenser and the break-down voltage of the gap being so proportioned that a plu- 40 rality of condenser `discharges occur for each pulsation of the feed current, said condenser discharges occurring in groups separated by periods of substantially no. gap activity, thereby causing the in duced oscillations to be likewise divided Vinto groups having an audible group frequency corresponding tothe frequency of the feed current pulsations,.substantiallyras described. i

9. Apparatus for-producing electrical oscillations, comprising an oscillation circuit,

and means for producing oscillations therein comprising a discharge circuit including a condenser and a discharge gap, and an v alternating c urrent generator for supplying a feed current having peaks separated by periods of substantially no current activity, comparable in duration to the peaks of the current alternations, ythe capacity o f the condenser and break-downvoltage of the gap being-so proportioned that a plurality of condenser discharges occur at each alternation of the feed current, said condenser discharges occurring in discrete groups corresponding to the peaks of the feed current y discrete and separated by periods of substantially no gap activity corresponding to the periods of substantially no feed current activity, substantially las described.r

l0. Apparatus for producing electrical oscillations,'comprising an oscillation circuit,

and means for producing oscillationstherein, comprising a discharge circuit including a condenser and a discharge gap, and means for supplying to the condenser a pulsation feed current having its pulsations separated by intervals of little, if any, current flow, the duration of such current pulsations and intervals being of the saine oider of magnitude, the capacity of the condenser andthe break-down voltage of the' gap being so proportioned that a plurality of condenser dispulsating feed current having its pulsations' separated'by periods in which the current flow, if any, is insufficient to cause any material activity at the discharge gap, the capacity of the condenser and break-down voltage of the gap being so proportioned with relation to the feed current that a plurality of condenser discharges occur for each pulsation of 'the feed current separated ice into discrete groups by periods of sub- 'I stantially no described.

.12. Apparatus for producing electrical oscillations, comprising an oscillation circuit, and means fegr producing oscillations therein comprising a `discharge circuit` in-' cluding a condenser and a discharge gap, and means for supplying to the Acondenser a pulsating feed current of such a wave shape and of such strength with relation to the capacity and break-clown voltage of the gap activity, substantially as gap that a plurality ,of closely spaced con-- denser discharges occur at each wave peak forming groups separated by periods of substantially no gapl activity between the Vwave peaks, substantially as described.

13. Apparatus for producing and -ra diating electrical oscillations having an audible group frequency, comprising a radiating circuit and means for producing oscillations therein including a circuit having a condenser and a discharge" gap. and means for supplying to the condenser a pulthe gap and occurring at such timed intervals that the condenser discharges form discrete groups of a plurality of condenser discharges each, separated by periods of substantially no gap activity, each group having'a sul'licient number of discharges to produce a clear tone in the telephones of a receiving station, substantially as described.

14. Apparatus for producing and radiating electrical oscillations having an audible group frequency, comprising a radiating circuit and means for producing oscillations therein, including a circuit having a condenser and a discharge gap, andan alternating current generator for supplying to the condenser an alternating feed current having such wave shape that the condenser discharges occur in discrete groups separatedby periods of substantially no gap activity, the capacity of the condenser and the break-down voltage of the gap being so pro` portioned with relation to the feed current that a suicient number of discharges occur for each alternation of the feed current to produce a clear tone of double the generator frequency in the telephones at a receiving station, substantially as described.

15. Apparatus for producing and radiat- Aing electrical current having an audible group frequency comprising an oscillation circuit and means for producing oscillations therein including a circuit Yhaving ,a condenser and a discharge gap, and means for supplying to the condenser a pulsating feed current of audible frequency having its current pulsations separatedy by intervals comparable in duration to the current pulsations during which 'intervals the current flow, if

any, is insufficient to cause any material activity at the dischar e gap, the capacity of the condenser and reak-down voltage of mitting the condenser to discharge a plurality of times during each pulsation of its feed current, whereby the condenser discharges occur in discrete groups corresponding to the feed current pulsati`ons,ithe groups being separated b intervalsV corresponding to the intervals o substantially no feed current flow, substantially as described.

17. The method of oscillations having anv audible group frequency, comprising charging a condenser with a pulsating feed current having its pulsationsrecurring with an audible frequency and separated by intervals of substantially no current flow, such intervals being of approximately the same order of magnitude as the duration of the current pulsations, and permitting the condenser to discharge a plurality of times during each pulsation of its feed current whereby the condenser discharges occur in discrete groups corresponding to the feed current pulsations and separated from preceding and succeeding groups by inactive periods, substantially as described.

In testimony whereof, we have hereunto set our hands.

FULTON CUTTING. BOWDEN WASHINGTON.

- producingv electrical 

